Vehicles refer to agricultural equipment, construction equipment, tractors, harvesters, combines, and other off-road vehicles. A location-determining receiver (e.g., Global Positioning System receiver) is one of the most useful navigation sensors for user-assisted navigation or autonomous operation of vehicles. However, the location-determining receiver alone typically does not provide roll and pitch angular data of the vehicle. In hilly terrain or other work areas that are not generally flat, the absence of roll and pitch data may contribute to less navigational control of a vehicle than is desired or necessary to follow a generally linear path or another path to a target degree of precision.
To overcome the limitations of the location-determining receiver, additional sensors, such as fiber-optic gyros and accelerometers, may be associated with the location-determining receiver to determine roll and pitch data for the vehicle during its operation. The additional sensors and data processing for processing the sensed data tends to add additional cost to the vehicle. Further, the additional sensors are generally capable of measuring the current posture (e.g., current roll and pitch) of the vehicle, but not predicting the anticipated posture (e.g., future roll and pitch) of the vehicle. Because of the time delay between sensing of the roll and pitch data and acting upon the sensed data, the additional sensors may not provide a sensible solution for improved navigational control of a vehicle. Therefore, a need exists for a vehicular guidance system having compensation for variations in ground elevation.